1. Field of the Invention
The present invention relates to a system and a method for identifying and tracking samples of biological material during the preparation of samples of the material for microscopic inspection. The present invention more particularly relates to a system and a method which uses color-coding to identify and track animal or plant tissue samples during the preparation of samples of that tissue for microscopic inspection, and the color-coded embedding media and microscope slides used therewith.
2. Description of the Invention Background
The tracking of multiple samples of biological tissue while preparing that tissue for microscopic evaluation has always presented a problem to laboratory personnel. Multiple samples of tissue may be obtained for microscopic evaluation from, for example, human patients or animals during biopsy, surgery, or autopsy. Typically, during preparation for such evaluation, these tissue samples are first placed in a refrigerated chamber and frozen in a matrix of an embedding medium composed of aqueous resins; the frozen sample/medium is then cut into thin sections on a microtome within the refrigerated chamber; the individual sections are positioned on glass microscope slides; the samples are further processed, usually by staining with one or a series of chemical solutions; and a glass coverslip is placed over the stained samples. This general preparation technique, including the use of a matrix of frozen aqueous embedding medium to encase the tissue sample, has been in use for at least the past thirty years.
Because of the numerous steps involved in preparing the samples, it is somewhat difficult to track the sources of multiple tissue samples. Tissue samples from the same organ of different patients are typically indistinguishable one from another. The materials used in the embedding and sectioning steps, and the cold temperatures involved, preclude labeling by writing on the samples themselves. When samples from more than one patient must be prepared and sectioned in a narrow time frame, or when one specimen must be divided into several parts for independent examination of each part, it is often difficult to distinguish between samples and mix-ups may occur while preparing the samples.
Other processes for preparing tissue samples for microscopic inspection are also known. In one such method, the tissue sample is embedded in a paraffin compound before sectioning. The paraffin-embedding procedure requires significantly more time and is more complex than the frozen embedding medium procedure and requires a certain time period wherein the tissue sample must be immersed in a fixative solution. Consequently, the quicker frozen embedding medium procedure is commonly employed when evaluation of the tissue sample is needed immediately, for example, while a surgical procedure is being performed. Because the tissue samples may be prepared quickly when using the frozen embedding medium procedure, the possibility that samples will be misidentified is magnified. Because the results of the microscopic inspection of the tissue may, for example, affect the course of ongoing surgery, the consequences of misidentification may be grave.
One method of tissue sample identification is often used during the above-mentioned paraffin-embedding procedure. In that procedure plastic tissue cassettes may be used to enclose the sample during and after processing. The tissue cassettes typically are composed of a material which allows labeling with, for example, a permanent marker. However, in preparing tissue samples which are embedded in a matrix of frozen embedding medium, the cold temperatures involved do not allow labeling of any specimen holders which may be used.
Although a need for some means of identifying tissue samples processed using a matrix of frozen aqueous embedding media has existed for at least the past thirty years, the problem remains. Accordingly, it is desirable to provide a method for quickly and easily identifying and tracking samples of biological material during the preparation of sections of that material for microscopic inspection. The method must allow identification of the material from the initial step of freezing the material in embedding medium to the final step of mounting and staining the material on microscope slides.